#include<stdio.h>
#include<unistd.h>
#include <stdlib.h>
#include<sys/types.h>

int main()
{
    pid_t pid;
    printf("Before:pid is %d\n",getpid());
    if((pid=fork())==-1) perror("fork()"), _exit(1);
    printf("After:pid is %d,fork return %d\n",getpid(),pid);
    sleep(1);
    return 0;
}